Most perceptual, cognitive, affective, and linguistic events are specified concurrently in different sensory modalities and are distributed across time. Time and its various temporal attributes such as contiguity, duration, rate, and rhythmic structure can be represented equally well across modalities and thus provide a major basis for the integration of the heteromodal attributes of multimodally represented events and objects. Empirical evidence indicates that human infants can perceive some of these intermodal temporal attributes and can use them to integrate heteromodal inputs. Indeed, it seems that this ability is part of a generalized perceptual mechanism that constrains perception by focusing the infant's attention on intermodally temporally integrated events. Given that intermodally integrated events are a fundamental part of the infant's everyday experience, understanding the processes underlying the development of such abilities is critical. Recently the PI put forth a sequential, hierarchic model that provides a theoretical framework for the study of the development of responsiveness to intermodal temporal relations. The model proposes that due to the differential informational complexity of the four different temporal intermodal relations, responsiveness to intermodal temporal contiguity, duration, rate, and rhythm emerges sequentially in that order. Furthermore, the differentiation and emergence of responsiveness to the more complex intermodal temporal relations is dependent on the prior emergence of responsiveness to the simpler relations. The purpose of the current project is to carry out a systematic investigation of the development of infants' responsiveness to intermodal temporal relations by studying responsiveness to intermodal temporal contiguity, duration, rate, and rhythm in infants between 1 and 12 months of age. The habituation/test technique, together with measures of attention, will be used to investigate developmental differences in infants' responsiveness to each of the four types of intermodal temporal relations. Based on the PI's model and its extensions, a series of 18 experiments is proposed to test various predictions arising from the model and its extensions. The results will: (a) explicate mechanisms underlying the anticipated developmental changes in responsiveness to intermodal temporal relations, (b) add to our understanding of the development of a process that enables infants to learn about the psychological unity of their experience, and (c) help further develop and refine measures of perceptual functioning that already have proved to have diagnostic utility in detecting aberrant developmental outcomes.